The airframes of modern aircraft are constructed from a wide variety of materials, including steel, aluminum and composites. While most airframe components are made from strong, rigid materials, in order to conserve weight, certain airframe components are made from relatively thin material layers attached to stiffening structures such as stringers. For example, the wing of a conventional tiltrotor aircraft includes a torque box structure formed from an upper skin, a lower skin, a forward spar and an aft spar. The upper and lower skins have stringers attached thereto that extend generally parallel with the longitudinal axis of the wing to provide stiffness and support to the skins. The stringers may have an I-beam cross section and are typically connected to the interior surface of the skins at reinforcement strips that provide support for the skins against catastrophic buckling, help to maintain the shape and contour of the skins, provide stiffness at the stringer load points and distribute pressure into the skins. In addition, the torque box structure typically includes multiple internal support members that provide horizontal structural strength to the forward and aft spars and the upper and lower skins.
It has been found, however, that the assembly of the torque box structure for conventional tiltrotor aircraft wings is complex and requires very tight tolerances. For example, the installation of numerous fasteners to the skins and other structural components is difficult and time consuming due to limited access to small interior spaces and complicated sealing requirements. Also, once the structural members are assembled, numerous foam details must be positioned between the structural members in the fuel bays to provide a smooth, ramped surface for the fuel components housed therein. In addition, it has been found, that the thickness of stringers as well as the multiple internal support members reduce the space available for fuel and other internal systems within the torque box structure.